Photo flash lamp



July 1, 1958 P. A. DELL ETAL PHOTO FLASH LAMP n? i I 1 iwfiwwww Inventors: Paul, A DeLL,

Conrad E. Becharid, 3 my fi y Then- A t tcqr neg.

, United States Patent PHOTO-FLASH LAMP Paul A. Dell, Highland Heights, and Conrad E. Bechard,

Lyndhurst, Ohio, assignors. toGeneral Electric Company, a corporation of New York ApplicationJune 5, 1957, Serial No. 663,748

4 Claims. (Cl. 67-31) Our invention relates to an. electric lamp, and more particularly, to an improved filament structure for an electrical photoflash lamp.

In one type of flash lamp in common use at present, the combustible light-producing material consists of a quantity of metal foil or filamentary material loosely arranged within the active portion of the bulb. To initiate the combustion of the foil in such lamp, suitable ignition means is provided therefor which comprises a resistance element or filament, parts of which are covered with primer paste and supported within the bulb in close proximity to the loosely arranged combustible metal filling by a conventional mount structure. The primer paste used is extremely sensitive and when the electrical circuit through the filament is energized, the heated filament promptly ignitesthe beadsof primer which, in turn, ignites the combustible material.

In another type of flash lamp currently on the market, the light-producing material consists solely of one or more beads of a readily ignitable light-producing material as the sole source of light, the beads or coatings preferably being disposed on the inner leads and partly on ignition filament of the lamp mount structure.

It is highly advantageous that the ignition means be operative to ignite and flash the lamp even under marginal conditions as where the batteries employed to supply the electrical current to the lamp are in a weakened or run-down condition, or even though the resistance of the electrical flashing circuit for the lamp be unduly high due to poor contacts or other causes. The probability of flashing the lamp is known in the art as flashability. Flashability has been improved in the past by decreasing the diameter of the filament and/or by changing the primer composition for increased sensitivity. In order to improve flashability further, it is desirable to insure deposition of some of the primer material directly on the filament, and even more, to deposit it at the point of the filament that would most likely burn out.

An object of the present invention is to provide an improved photoflash bulb.

A further object of the invention is to provide a photoflash bulb having improved flashability characteristics.

Further objects and advantages of our invention will become apparent as the following description proceeds and the features of novelty which characterize our invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Briefly stated, in accordance with the invention, a larger effective radius on the filament is created by replacing the round wire with a flattened surface having approximately a rectangular cross-section. This was based on the observation that since primer deposits readily on the lead tips but not readily on the much smaller filament, it is believed that the larger radius was the cause of the better deposits of primer.

The nature of the invention will best be understood ice when described in connection with the accompanying drawings, in which Fig. 1 is afilament mount having a filament in. accordance with the present invention; Fig. 2 is an assembled photoflash bulb employing the invention; and Fig. 3 is an enlarged view of a filament according to the invention and illustrating the filament in plan and elevation views.

A filament according to the present invention is shown in a beaded mount; however, it is to be understood that the present invention can be employed with any type of lamp mount. The mount is shown generally at 1. Such mounts preferably comprise a pair of lead-in wires 2 and 3, parallel portions of which are held together by a bead 4 of insulating material such as glass, and which support a. filament 5 at their inner ends. The inner ends of the lead-in wires 2 and 3 and the outer ends offilament 5 contain beads 6 and '7' of primer for igniting theassembled photoflash lamp. The outer ends of the lead-in wires 2 and 3 extend transversely to the inner ends and are bent back so as to be atan angle to the mid-portion and extend in opposite directions therefrom, thereby facilitating assembly of the mount with the bulb.

Referring now to Fig. 2, a photoflash lamp bulb or envelope 8 of light-transmitting material, is filled with. combustible material 9 such as shredded aluminum foil. The filament mount 1 is assembled in the bulb so that the beads of primer 6, 7 extend into the combustible material 9. The bulb 8 is filled with oxygen or other suitable combustion supporting gas and subsequently tipped off. The bulb 8 may be coated witha protective coating. of a suitable light-transmitting lacquer or varnish to thereby minimize cracking of the glass bulb on flashing and render the bulb substantially shatterproof.

The lamp may have any style base. Lead-in wire 2 is sealed through the wall of the glass envelope 8 and is secured to contact 10; while the other lead-in wire 3, which is also sealed through the wall of bulb 8, is secured to base structure 11 which serves as a second contact. Contact 10 is electrically isolated from base structure 11 by insulating material 12. In this manner an electrical circuit is maintained from contact 10 to lead-in wire 2, through the filament 5, through lead-in wire 3, and to the base structure 11.

As previously stated, a charge of current through the filament heats the filament sufficiently to ignite the primer material 6, 7, which in turn ignites the combustible material 9 within the bulb. However, under the conventional method of depositing primer by dipping the filament supporting end of the mount 1 into the primer, very little or no primer deposits on the small filament. The conventional filament presently commercially used consists generally of a straight round tungsten wire of small diameter and having high electrical resistance. It is believed that the roundness and smoothness of the wire is responsible for the failure of the primer to adhere thereto.

The filament 5 can be modified so that it will pick up primer along a portion of its length in addition to that deposited on the lead tips as indicated by beads 6 and 7. As illustrated in Fig. 3, the center portion of the filament is flattened to cause a small flat surface 13. If desired, the center portion of the filament may be both flattened and may simultaneously have a reduction in its cross-sectional area, thereby increasing the electrical resistance of the filament at this point and cause the filament to heat more rapidly at this flattened section. When the filament supporting end of the mount 1 is then dipped into primer for the purpose of picking up primer on the filament, a head 14 of primer will be picked up directly on the flattened portion of the filament 5 in addition to the beads 6 and 7 of primer that are deposited on the lead tips and the ends of the filament.

While we have described only certain preferred embodiments of our invention by Way of illustration, many modifications will occur to those skilled in the art. We, therefore, wish to have it understood that we intend in the appended claims to cover all such modifications as fall within the true spirit and scope of our invention.

What we claim as new and desire to secure by'Letters Patent of the United States is:

1. A flash lamp comprising a sealed light-transmitting envelope containing a combustion supporting gaseous .filling and a quantity of readily combustible material loosely arranged within the envelope, electric ignition means for said combustible material comprising a pair of lead-in wires sealed through the wall of and extending into said envelope, and an ignition filament within said envelope and having its opposite ends firmly secured to the inner ends of said lead-in wires to electrically connect the filament thereto, said filament having a portion thereof between said lead-in wi-res flattened into approximately a rectangular cross-section, beads of primer on said filament and lead-in wires where the filament is secured to the lead-in wires, and additional primer on the flattened portion of the filament.

2. A flash lamp comprising a sealed light-transmitting envelope containing a combustion supporting gaseous filling and a quantity of readily combustible material loosely arranged within the envelope, electric ignition means for said combustible material comprising a pair of lead-in wires sealed through the Wall of and extending into said envelope, and a round ignition filament wire within said envelope and having its opposite ends secured to the inner ends of said lead-in wires to electrically connect the filament thereto, said filament wire having a portion thereof between said lead-in wires flattened out of round, beads of primer on said filament and lead-in wires where the filament is secured to the lead-in wires, and additional primer on the flattened portion of the filament wire.

3. A flash lamp comprising a sealed light-transmitting envelope containing a combustion supporting gaseous filling and a quantity of readily combustible material, electric ignition means for said combustible material comprising a pair of lead-in wires sealed through the wall of and extending into said envelope, and an ignition filament within said envelope and having its opposite ends secured to the inner ends of said lead-in wires to electrically connect the filament thereto, said filament having a portion thereof between said lead-in wires flattened into approximately a rectangular cross-section, primer deposited on the filament and lead-in wire where the filament is secured to the lead-in Wires, and additional primer on the flattened portion of the filament.

4. A flash lamp comprising a sealed light-transmitting envelope containing a combustion supporting gaseous filling and a quantity of readily combustible material, electric ignition means for said combustible material comprising a pair of lead-in wires sealed through the Wall of and extending into the envelope, and an ignition filament within said envelope and having its opposite ends secured to the inner ends of said lead-in wires to electrically connect the filament thereto, said filament Wire having a portion thereof between said lead-in wires flattened out of round, and primer deposited on said fiattened portion of the filament.

No references cited. 

